Spatio-temporal distribution of Ricania shantungensis (Hemiptera: Ricaniidae) in chestnut fields: implications for site-specific management.
Chestnut is one of most important forest products in Korea. However, Ricania shantungensis, an invasive species, has been increasingly causing economic damage to chestnut. To increase management efficiency of R. shantungensis in chestnut fields, its spatio-temporal distributions were analyzed using spatial analysis by distance indices (SADIE) and semivariogram. Experiments were conducted by observing selected, marked, and geo-referenced trees in two commercial chestnut fields for each developmental stage (i.e., spring egg, nymph, adult, and fall egg) of R. shantungensis from 2017 to 2019. Spatial distributions of R. shantungensis were statistically (P < 0.05) aggregated except for its nymphal stage. Spatial associations of its distributions also showed the statistically (P < 0.05) positive associations regardless of years or developmental stages except for the spatial relationship between egg and nymphal stages. These results indicated that site-specific management for R. shantungensis would be applicable. In application of site-specific management for R. shantungensis, the distance of spatial dependence for nymphs, 60 m, should be considered to minimize reoccurrence possibility and additional samplings. Incorporating site-specific management into pest control program of R. shantungensis could increase its control efficiency in chestnut fields.